Traditionally, pitched roofs include a protective covering, such as tiles or shingles, presented on a roof board or “deck” that covers an unconditioned space or “attic.” The attic can serve as a buffer to a conditioned, living space below the attic. It can desirable to attempt to maintain the temperature of the attic, through the use of ventilation, so that the temperature of the attic is at or near the outside environmental air temperature.
Such ventilation can be done using soffit vents and roof or ridge vents. Even if such vents are included, however, they can be inadequate and/or deteriorate with the age of the home. As a result, roofs can develop unwanted thermal heat loads (heat gains) in the conditioned, living space in the summer season and the removal of thermal heat (heat loss) in the conditioned, living space during the winter period.
Furthermore, many heat loads can be caused by “radiant” heat, which can cause high cooling energy costs in buildings, particularly in warm southern climates that receive a high incidence of solar radiation. It is not uncommon for the air temperature within a space adjacent to or under a roof to exceed the ambient outside air temperature by 40° F. (about 22° C.) or more, due to absorption of solar energy by the roof. This can lead to a significant energy cost for cooling the living spaces of a building to a comfortable living temperature. Most homes do not have solutions for managing or reducing radiant heat.
Also, in colder climates, traditional roofs can have inadequate air flow from the soffit to the peak exit can lead to ice build-up or “ice dams” at the lower eaves area. Ice dams form when there is snow on the roof and removal of thermal heat (heat loss) of the conditioned space, or heat from solar gain absorbed by the portions of the roof that are not snow covered, melts snow on the roof. The resulting water travels down the roof to lower portions of the roof that are below 32° F. (usually at the eves) and the water refreezes. The ice then forms a small dam that slowly builds up and, eventually, the water can back up behind the dam. This backed-up water can then work its way under the shingles and leak into the space below. Poor unconditioned space ventilation in colder climates can also lead to build up of frost and condensation that form on the underside of the roof.